2019 SDN上级第五次作业

1.浏览RYU官网学习RYU控制器的安装和RYU开发入门教程，提交你对于教程代码的理解，包括但不限于：

• 描述官方教程实现了一个什么样的交换机功能？

  答：官方教程实现了一个将接收到的数据包发送到所有端口的交换机功能

• 控制器设定交换机支持什么版本的OpenFlow？

  答：控制器设定交换机支持OpenFlow 1.0

• 控制器设定了交换机如何处理数据包？

  答：'''@set_ev_cls(ofp_event.EventOFPPacketIn, MAIN_DISPATCHER)'''
  
  答：当Ryu收到OpenFlow交换机送来的packet_in消息时调用新增方法packet_in_handler，set_ev_cls的第一个参数也声明了

2.根据官方教程和提供的示例代码（SimpleSwitch.py），将具有自学习功能的交换机代码（SelfLearning.py）补充完整

• 代码链接

  如下是补充完整代码：

from ryu.base import app_manager
from ryu.controller import ofp_event
from ryu.controller.handler import MAIN_DISPATCHER
from ryu.controller.handler import set_ev_cls
from ryu.ofproto import ofproto_v1_0

from ryu.lib.mac import haddr_to_bin
from ryu.lib.packet import packet
from ryu.lib.packet import ethernet
from ryu.lib.packet import ether_types
from ryu.lib.packet import ipv4

class SimpleSwitch(app_manager.RyuApp):
	# TODO define OpenFlow 1.0 version for the switch
	# add your code here
	OFP_VERSIONS = [ofproto_v1_0.OFP_VERSION]

	def __init__(self, *args, **kwargs):
		super(SimpleSwitch, self).__init__(*args, **kwargs)
		self.mac_to_port = {}

	def add_flow(self, datapath, in_port, dst, src, actions):
		ofproto = datapath.ofproto

		match = datapath.ofproto_parser.OFPMatch(
            in_port=in_port,
            dl_dst=haddr_to_bin(dst), dl_src=haddr_to_bin(src))

		mod = datapath.ofproto_parser.OFPFlowMod(
            datapath=datapath, match=match, cookie=0,
            command=ofproto.OFPFC_ADD, idle_timeout=0, hard_timeout=0,
            priority=ofproto.OFP_DEFAULT_PRIORITY,
            flags=ofproto.OFPFF_SEND_FLOW_REM, actions=actions)
		# TODO send modified message out
		# add your code here
		datapath.send_msg(mod)
	@set_ev_cls(ofp_event.EventOFPPacketIn, MAIN_DISPATCHER)
	def _packet_in_handler(self, ev):
		msg = ev.msg
		datapath = msg.datapath
		ofproto = datapath.ofproto

		pkt = packet.Packet(msg.data)
		eth = pkt.get_protocol(ethernet.ethernet)

		if eth.ethertype == ether_types.ETH_TYPE_LLDP:
			# ignore lldp packet
			return
		if eth.ethertype == ether_types.ETH_TYPE_IPV6:
			# ignore ipv6 packet
			return       

		dst = eth.dst
		src = eth.src
		dpid = datapath.id
		self.mac_to_port.setdefault(dpid, {})

		self.logger.info("packet in DPID:%s MAC_SRC:%s MAC_DST:%s IN_PORT:%s", dpid, src, dst, msg.in_port)

		# learn a mac address to avoid FLOOD next time.
		self.mac_to_port[dpid][src] = msg.in_port

		if dst in self.mac_to_port[dpid]:
			out_port = self.mac_to_port[dpid][dst]
		else:
			out_port = ofproto.OFPP_FLOOD

		# TODO define the action for output
		# add your code here
		actions = [datapath.ofproto_parser.OFPActionOutput(out_port)]

        # install a flow to avoid packet_in next time
		if out_port != ofproto.OFPP_FLOOD:
			self.logger.info("add flow s:DPID:%s Match:[ MAC_SRC:%s MAC_DST:%s IN_PORT:%s ], Action:[OUT_PUT:%s] ", dpid, src, dst, msg.in_port, out_port)
			self.add_flow(datapath, msg.in_port, dst, src, actions)

		data = None
		if msg.buffer_id == ofproto.OFP_NO_BUFFER:
			data = msg.data

		# TODO define the OpenFlow Packet Out
		# add your code here
		out = datapath.ofproto_parser.OFPPacketOut(datapath=datapath, buffer_id=msg.buffer_id, in_port=msg.in_port,  actions=actions, data=data)
		datapath.send_msg(out)
		print ("PACKET_OUT...")

3.在mininet创建一个最简拓扑，并连接RYU控制器

拓扑代码如下：

#!/usr/bin/python
#Creating Inernet Topo

from mininet.topo import Topo

class MyTopo(Topo):

    def __init__(self):

        # initilaize topology
        Topo.__init__(self)

        # add hosts and switches
        h1 = self.addHost('h1')
        h2 = self.addHost('h2')

        s1 = self.addSwitch('s1')

        # add links
        self.addLink(h1, s1, 1, 1)
        self.addLink(h2, s1, 1, 2)

topos = {'mytopo': (lambda: MyTopo())}

使用命令连接控制器

ryu-manager SelfLearning.py

4.验证自学习交换机的功能，提交分析过程和验证结果

创建一个拓扑后，如果没有ryu控制器连接，pingall命令的时候是不通的



通过ovs-ofctl dump-flow命令查看s1所有流表时显示无流表存在



接入ryu控制器之后使用pingall命令的时候可以ping通，且s1存在多个流表

5.写下你的实验体会

感觉这次实验除了Ryu难装其他还是很轻松的，这个实验很有意思，代码要看好久才能懂得一点···希望自己加油吧！